1. Field of the Invention
The present invention relates to a method and apparatus for detecting the media type of a media. More particularly, the present invention relates to a method and apparatus for detecting media type by aligning a media type detector onto a media, with sufficient force, in a media manipulation or sensing apparatus.
2. Description of the Related Art
Typically, media manipulation or sensing apparatuses operate in different modes based on the presence of different types of media. A media manipulation or sensing apparatus may operate in a different mode if the media type is of a high glossy type, like a transparency media type, compared to when the media type is of a low glossy type, like plain paper. For example, in a printing environment, certain parameters of printing onto a media are adjusted based upon the media type determination. Typically, in the printing environment, a user must manually indicate to a printing apparatus what type of media is present. Alternatively, some printing systems xe2x80x9cpick,xe2x80x9d or grab, the media and advance it through the printing system, and then determine the type of media, format the parameters for printing thereon, and proceed with printing onto the media. However, these systems are not usually desirable, as the printing system cannot perform the procedure to determine what type of media is being printed on until after advancing the media, which reduces the throughput of media in the printing system. Knowing the media type before picking allows one to adjust certain picking parameters so as to optimize the picking process for that media. This is something that is now done when the user manually indicates to the printing system what type of media is present. Other current media sensors do not provide this ability.
Optical methods and apparatuses previously implemented for such media type detection have included media type detectors having multiple sensors detecting an amount of light reflected off a media. In addition, in one media type detector, as illustrated in FIG. 1, when light source 10 irradiates media 5, light reflecting off media 5 is detected by diffuse sensor 20 and specular sensor 15.
The glossiness of media 5 may then be determined by measuring the ratio of the detected diffuse I(D) and specular I(S) light intensities. Glossier papers tend to reflect specularly more than diffusely, thus a media detecting ratio of I(S)/I(D) can be used to determine the glossiness of media 5, from which the type of media can be determined. Typically, before measuring the media detecting ratio I(S)/I(D), a ratio table is developed, wherein media detecting I(S)/I(D) ratios are stored for a corresponding multitude of different types of media. By referencing back to this ratio table after measuring media detecting ratio I(S)/I(D), corresponding types of media can be differentiated. Typically the determination of a media type according to the media detecting ratio I(S)/I(D) can be accomplished for an overall system in a determining portion by hard wiring or by software in a processing unit.
As illustrated in FIG. 1, diffuse sensor 20 may be arranged at a position normal from media 5, but may be anywhere other than close to an incidence angle a, and specular sensor 15 should be arranged at a position along a clockwise incidence angle a from normal, with light source 10 being arranged at a position along a counterclockwise incidence angle a from normal.
FIGS. 2A-2C illustrate intensity distributions for different types of media. With a perfectly diff-use media type in FIG. 2A, the intensity distribution is substantially equal in all reflected directions. Whereas, with low glossy and high glossy media types shown in FIGS. 2B and 2C, respectively, the intensity in the specular direction is larger than the reflected intensity in non-specular directions.
It is important to keep the light source and the sensors aligned correctly to the media and to minimize any extraneous external light. As noted above with the incidence angle configuration of the light source and specular sensor, a specular light sensor measures the amount of light that reflects off the media at an angle equal to the angle of the radiating light from the light source. When the media is tilted, the measured specular intensity will change since the angle of incidence for the radiating light from the light source has changed. For the specular sensor to detect an accurate specular intensity signal the media should be in a particular position in relation to the light source and specular sensor. As illustrated in FIG. 2C, the specular intensity lobe is very narrow, and if the media is tilted, the specular sensor may not detect an accurate specular intensity as the specular lobe will partially or completely miss the specular sensor. Compared to the specular intensity, the diffuse intensity is not very sensitive to media tilt.
A media tilt can generate a substantial amount of error in the media detecting ratio I(S)/I(D). The amount of error can be such that a media type determination may be incorrect. Therefore, for reliable performance of the media detector, the orientation of the media with respect to the light source and specular sensor is crucial. FIG. 3A illustrates an example where the media is not tilted, resulting in zero error, whereas in FIG. 3B, as the media is tilted relative to the light source and specular sensor, the misalignment angle is twice the tilt angle
In a printing system, this tilting of the media can be generated by the influences of static electricity, as well as other factors, on paper in a paper tray. These influences can cause the paper to lift or roll in different areas, and thereby generate the above tilting of the media. Typical media transport systems include conductive materials which generate static electricity. For example, paper passing over a plastic platen will generate a static electric charge. Further, continuing with the paper example, paper stored in a paper tray is usually not held very tightly or may even freely float therein, and therefore, may slide down in the paper tray or may generate a natural curl or waviness with humidity changes. These disclosed problems all detail potential sources of tilting in a media, which must be accounted for to determine media types accurately.
Previous examples of media detectors having an element of alignment include Lowrey, U.S. Pat. No. 1,917,379, where a sensor is applied near a web to detect unevenness, Tajima, U.S. Pat. No. 4,739,605, where a spring loaded reflector is moved by an insertion of media, thereby indicating a presence of media, and in Yoshida et al., U.S. Pat. No. 5,758,982, where an end of a roll of paper is measured by a photosensor being applied against the roll of paper, by a spring system, and by measuring a change in intensity of reflected light to thereby detect an end of the roll of paper. However, none of these references disclose or overcome the aforementioned problems with previous media type detectors.
Therefore, it is necessary to overcome these potential errors by aligning the media detector to compensate for tilting of a media relative to the media detector.
An object of the present invention is to provide a method and apparatus for detecting the media type of a media by aligning a media detector onto a media, with sufficient force, in a media manipulation or sensing apparatus.
A further object of the present invention is to provide a media manipulation apparatus having a housing sled including at least two light sensors, a force applying mechanism to force the housing sled into contact with a media, and a determining unit to determine a media type of the media based on a ratio of detected light intensities measured by the light sensors while the housing sled is in contact with the media.
Another object of the present invention is to provide a media sensing apparatus having a housing sled including at least two light sensors, a force applying mechanism to force the housing sled into contact with a media, and a determining unit to determine a media type of media based on a ratio of detected light intensities measured by the light sensors while the housing sled is in contact with the media.
A further object of the present invention is to provide a media type detector, for determining a type of media based on a ratio of a detected specular light intensity to a detected diffuse light intensity, including a housing sled including at least a diffuse light sensor and a specular light sensor, and a force applying mechanism to force the housing sled into contact with a media during a detection of the detected specular light intensity and detected diffuse light intensity.
Another object of the present invention is to provide a method of media type detection including applying a media type detector into contact with a media, with the media type detector having a plurality of light intensity sensors, detecting at least two light intensities, and determining a media type of the media by comparing the detected light intensities.